Delayed cerebral vasospasm is not reversible by aminophylline, nifedipine, or papaverine in a "two-hemorrhage" canine model.

Angiographic spasm of cerebral arteries was produced in dogs by successive injections of cisternal blood 48 hours apart. Angiograms were taken before and after each cisternal injection. There was progressively greater angiographic vasospasm of the basilar artery. Intravenous aminophylline, 10 mg/kg/hr, reversed vessel constriction on the 1st and 3rd day after one injection of cisternal blood. On the 5th day after two blood injections (on Day 1 and Day 3), intravenous aminophylline, nifedipine (1 mg/kg), and intra-arterial bolus injection of 2 mg/kg papaverine failed to reverse the constriction. The intractable constriction produced in this model resembles that found in patients. The calcium antagonist, nifedipine, is as ineffective as the more traditional vasodilators in reversing vasospasm in this model.